Recently, monoclonal antibodies labeled with the radionuclide iodine-131 have been used for the detection of tumors. Goldenberg reported the imaging of tumors using monoclonal antibodies [Journal of Nuclear Medicine, 24, 360-362 (1983)] while Larson, et al. reported melanoma imaging using iodine-131 labeled monoclonal antibodies [Journal of Nuclear Medicine, 24, 123-129 (1983)]. One of the problems that has been encountered with such radionuclide labeled monoclonal antibodies has been that the labeling inactivates the antibody because the radionuclide attaches at or near the antigen-binding sites. One approach to overcoming this problem is to employ bi-functional chelates that are capable of covalently binding to the antibody and also complexing with a metallic radionuclide. Krejcarek, et al. discuss the covalent attachment of chelating groups to macromolecules, [Biochemical and Biophysics Research Communications, 77, 581-585 (1977)].